Week 02 RNA: The Sky

1. On clear, moonless nights far from city lights, more than ____ stars may be visible to your naked eye, alongwith the whitish band of light that we call the ____ ____

2,000, Milky Way

We usually refer to such patterns as constellations, but to astronomers the term has a more precise meaning: A ____ is a ____ ____ ____ ____with well-defined borders; the familiar patterns of stars merely help us locate these constellations.

Constellation, Region of the Sky

For reference, we identify two special points and two special circles on the celestial sphere.

1. The ___ ___ ___ is the point directly over Earth's North Pole.

North Celestial Pole

For reference, we identify two special points and two special circles on the celestial sphere.

2. The ___ ___ ___ is the point directly over Earth's South Pole

South Celestial Pol

For reference, we identify two special points and two special circles on the celestial sphere.

3. The ___ ___, which is a projection of Earth's equator into space, makes a complete circle around the ___ ___

Celestial Equator, Celestial Sphere

For reference, we identify two special points and two special circles on the celestial sphere.

4. The ___ is the path the Sun follows as it appears to circle around the celestial sphere once each year. It crosses the celestial equator at a 23½° angle, because that is the ___ of Earth's ___

Ecliptic, Tilt, Axis

Our galaxy is shaped like a ____ ____ with a _ in the middle. We view the universe from our location a little more than halfway out from the center of this "pancake." In all directions that we look within the pancake, we see the many stars and vast interstellar clouds that make up the Milky Way in the night sky; that is why the_ ____ ____ makes a full circle around our sky

Thin Pancake, Bulge, Band of Light

Your ____ ____ - the sky as seen from wherever you happen to be standing - appears to take the shape of a____ or ____

Local Sky, Hemisphere, Dome

The boundary between Earth and sky defines the ____. The point directly overhead is the ____.

Horizon, Zenith

The ____ is an imaginary half-circle stretching from the horizon due south, through the zenith, to the horizon due north. We can pinpoint the position of any object in the local sky by stating its direction along the horizon (sometimes stated as ____, which is degrees clockwise from due north) and its ____ above the horizon

Meridian, Azimuth, Altitude

The ____ ____ of an object is the angle it appears to span in your field of view. For example, the angular sizes of the Sun and the Moon are each about ½°. Note that angular size does not by itself tell us an object's true size, because angular size also depends on ____. The Sun is about 400 times as large in diameter as the Moon, but it has the same angular size in our sky because it is also about 400 times as far away.

Angular Size, Distance

The ____ ____ between a pair of objects in the sky is the angle that appears to separate them. For example, the angular distance between the "pointer stars" at the end of the Big Dipper's bowl is about 5° and the angular length of the Southern Cross is about 6°. For greater precision, we subdivide each degree into ____ ____ (symbolized by ') and each arcminute into ____ ____ (symbolized by ").

Angular Distance, 60 Arcminutes, 60 Arcseconds

Stars near the north celestial pole are ____, meaning that they remain perpetually above the horizon, circling (counterclockwise) around the north celestial pole each day.

Stars near the south celestial pole ____ ____ above the horizon at all.

Circumpolar, Never Rise

All other stars have daily circles that are partly ____ the horizon and partly _, which means they appear to_ in the east and ____ in the west.

Above, Below, Rise, Set

____ measures north-south position on Earth and ____ measures east-west position. Latitude is defined to be 0° at the equator, increasing to 90°N at the North Pole and 90°S at the South Pole.

Latitude, Longitude

The ____ of the celestial pole in your sky is equal to your ____. For example, if you see the north celestial pole at an altitude of 40° above your north horizon, your latitude is 40°N

Altitude, Latitude

The night sky ____ throughout the year because of Earth 's changing position in its orbit around the Sun. From our vantage point on Earth, the annual orbit of Earth around the Sun makes the Sun appear to move steadily eastward along the ecliptic, with the stars of different constellations in the background at different times of year. The constellations along ____ ____ make up what we call the zodiac; tradition places ____ ____ along the zodiac, but the official borders include a ____ constellation, Ophiuchus

Changes, The Ecliptic, 12 Constellations, 13th

Most people are aware that the North Star, Polaris, is a special star. Contrary to a relatively common belief, however, ____ ____ ____ ____ ____ star in the sky. More than 50 other stars are just as bright or brighter. Polaris is special not because of its brightness, but because it is so close to ____ ____ ____ ____ and therefore very useful in navigation.

It is not the Brightest, The North Celestial Pole